Wind turbine blade root attachment system and method of manufacture

ABSTRACT

Devices, systems, and methods of manufacturing wind turbine root attachment are provided. In various embodiments, an assembly for wind turbine root attachments includes a bushing, a core, and a filler. The bushing includes a body having cutouts extending from the proximal end to the distal end on either side of the bushing and a core cutout at the distal end. The bushing further includes an ear disposed at the proximal end of the bushing and within the first cutout. The core includes two wedges where the thick end of each wedge abut one another. The thin end of the proximal wedge is disposed within the core cutout and the core includes cutouts extending from the proximal end to the distal end on either side of the core. The filler is disposed within the cutout on the side of the assembly having the ear.

CROSS REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of priority under 35 USC 119 to U.S.Provisional Application No. 62/734,546 filed Sep. 21, 2018, the entirecontents of which are hereby incorporated by reference.

BACKGROUND

Embodiments of the present disclosure relate to devices, assemblies,systems, and methods of manufacturing wind turbine blade rootattachments.

BRIEF SUMMARY

According to embodiments of the present disclosure, devices, systems,and methods of manufacturing wind turbine blade root attachments areprovided. In various embodiments, an assembly includes a bushing, acore, and a filler. The bushing includes a body having a proximal endand a distal end, a first cutout extending from the proximal end to thedistal end on a first side of the bushing, a second cutout extendingfrom the proximal end to the distal end on a second side of the bushingand a core cutout at the distal end, and an ear disposed at the proximalend of the bushing and within the first cutout. The core has a proximalend and a distal end and includes a first wedge and a second wedgedistal to the first wedge. Each wedge has a thick end and a thin end,and the thick end of the first wedge abuts the thick end of the secondwedge. The thin end of the first wedge is disposed within the corecutout and the core includes a third cutout extending from the proximalend to the distal end on a first side of the core and a fourth cutoutextending from the proximal end to the distal end on a second side ofthe core. The filler is disposed within the first cutout and the thirdcutout and contacts the ear.

In various embodiments, a system for wind turbine blade root attachmentincludes a plurality of sub-assemblies arranged in a ring. Thesub-assemblies each include a bushing, a core, and a filler, asdescribed above.

In various embodiments, a method of forming a wind turbine rootattachment system according to embodiments of the present disclosureincludes providing a plurality of sub-assemblies, where each of thesub-assemblies includes a bushing, a core, and a filler, as describedabove. The plurality of assemblies is formed into a ring.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

FIG. 1 illustrates an exemplary assembly, shown in an exploded view, forwind turbine blade root attachment according to embodiments of thepresent disclosure.

FIG. 2 illustrates a cross-section of an exemplary system for windturbine blade root attachment according to embodiments of the presentdisclosure.

FIG. 3 illustrates a method of wind turbine blade root attachmentaccording to embodiments of the present disclosure.

FIG. 4 illustrates a portion of an axial view of root bushing, depictingthe gap present between adjacent circular root bushings.

FIG. 5 illustrates a segment UD-fiber which can be cut according to thepattern shown to form a filler in accordance with the presentdisclosure.

FIGS. 6-9 illustrates additional views of an exemplary embodiment of theroot attachment in accordance with the present disclosure.

DETAILED DESCRIPTION

Modern wind turbine rotor blades are built from fiber-reinforcedplastics as fiber-reinforced plastics have high strength-to-weightratios. A rotor blade typically includes an airfoil shape having arounded leading edge and a sharp trailing edge and the blade includes ablade root that connects to a hub of the turbine. Multiple rotor bladesare connected at the respective blade root to the hub to create the windturbine. The blade root includes a plurality of root bushings set withinthe fiber-reinforced polymer that provides reinforcement to the blade.Bolts are engaged with threads in the root bushings to connect the bladeroot to the hub.

In a wind turbine, the attachment of the root section of the rotorblades to the hub of a wind turbine is a critical joint where stressestend to concentrate from external forces on the blade, such as gravityand wind. Thus, the root section of the blade must be stable enough totransfer forces from the wind turbine blade into the hub to therebyrotate the hub and generate electrical energy. As an interface to thehub, metal parts may be used which are inserted or attached in otherways to the very end of the root section. For instance, U.S. Pat. No.4,915,590 (the entire contents of which are hereby incorporated byreference) discloses use of so-called sucker rods which are placedinside of the main body of a rotor blade and into which bolts can bescrewed which connect an interface section of the hub with the rotorblade itself. The sucker rods can be glued into the main body, forexample, and also include threads inside to receive the bolts comingfrom the hub.

Conical cylinders may also be used with threaded holes for a rootattachment system. The rotor blade is then adhered to the conicalcylinder either by gluing or by placing a curing laminate directly incontact with the metal root. The conical cylinder may for instance befabricated of aluminum.

Some root attachment systems utilize multiple hollow cylinders asbushings disposed around a ring attachment. Other root attachmentsystems may use square bushings. One or more layups of fiber reinforcedpolymer is applied over the ring of cylindrical (or square) bushings.Because of the shape of the cylindrical (or square) bushings, when thebushings are positioned around a ring, space or gaps are formed betweeneach of the individual bushings. This space between the bushings maydifficult to fill when laying up a fiber reinforced material around thering. Furthermore, any unfilled gaps can jeopardize the structuralintegrity and performance of the blade. FIG. 4, which shows a portion ofan axial view of root bushing, depicts the gap present in suchcylindrical (or square) root bushing designs.

Accordingly, a need exists for a blade root attachment system thatgeometrically fills all void space when multiple bushings are arrangedtogether in a ring, thereby reducing the amount of material used andincreasing strength properties of the blade.

In general, assemblies of the present disclosure include a bushing thatis generally cuboid-shaped having a cylindrical cutout on a first side,a cylindrical cutout on a second, opposite side, and a wedge-shapedcutout at a distal end. In various embodiments, the cylindrical cutoutson either side have substantially equal radii. In various embodiments,the cylindrical cutouts may have different radii.

On one of the sides, the bushing includes a cylindrically-shaped earextending circumferentially outwardly. The ear may be integral with thebushing or may be a separate component that is installed in the bushing,e.g., by adhesives or fixation devices (e.g., screws). In variousembodiments, the ear may be integrally formed into the bushing by, e.g.,machining the cutout. In various embodiments, the radius of the ear maybe substantially equal to the radius of the cutout. In variousembodiments, the radius of the ear may be different (larger or smaller)than the radius of the cutout. In various embodiments, the bushing mayinclude a threaded aperture that is configured to receive a screw forconnecting the bushing to a wind turbine rotor hub. The aperture may bealigned along a longitudinal axis of the bushing. In some embodimentsthe bushing can be formed from a casting processes, which providesflexibility in the component design and low cost manufacturability.

The assembly may include a core that is generally formed from a first,proximal wedge and a second, distal wedge. In various embodiments, thewedges may be the same or different sizes. In various embodiments, thecore may be made of a polymer foam, e.g., polyurethane foam. In variousembodiments, the thick ends of each wedge may abut one another. Invarious embodiments, the core may be manufactured as a single piece oras two separate pieces that are subsequently connected at the thickends. In various embodiments, the thin end of the first wedgecorresponds to the shape of the cutout of the bushing such that thefirst wedge matingly engages the bushing. In various embodiments, thefirst wedge of the core may include a first cutout on one side and asecond cutout on the opposite side that are shaped as conical cutouts.In various embodiments, when the first wedge is inserted into thebushing, the cutout of the first wedge and the cutout of the bushingtogether form a cylindrical cutout. In various embodiments, similar tothe first wedge, the second wedge may include a first cutout on one sideand a second cutout on the opposite side that are shaped as conicalcutouts.

In various embodiments, the assembly may include a filler having aproximal, cylindrical portion and a distal, conical portion. In variousembodiments, the cylindrical portion of the filler may correspond to(and matingly engage with) the side cutouts of the bushing and first,proximal wedge. In various embodiments, the conical portion of thefiller may correspond to (and matingly engage with) the side cutouts ofthe second, distal wedge. In various embodiments, the filler may be madeof glass fiber-reinforced polymer or any other suitable fiber-reinforcedpolymer. In some embodiments the filler is made of dry glass (e.g.Unidirectional Glass) and is injected with the rest of the blade.

A system of the present disclosure generally includes a plurality of theroot attachment assemblies described above positioned in a ring. Invarious embodiments, each of the assemblies includes a bushing, a core,and a filler as described above. In various embodiments, the filler ofeach assembly matingly engages the ear and cutouts of another assembly,thus filling the void space between the two adjacent assemblies.

In various embodiments, the bushing, core, and/or filling may be madeout of any suitable metal as is known in the art. In variousembodiments, the bushing, core, and/or filling may include a metal, suchas, for example, aluminum, steel, stainless steel, titanium, tantalum,tungsten, or any suitable combination of metals (e.g., a metal alloy).In various embodiments, the bushing, core, and/or filling may include apolymer, for example, polyethylene, polyurethane, polyethyleneterephthalate, polyvinyl chloride, etc. In various embodiments, thebushing, core, and/or filling may be made by machining (e.g., CNCmachining), 3D printing (e.g., using Direct Metal Laser Sintering (DMLS)and Fused Deposition Modeling (FDM)), open molding, closed molding,resin infusion, compression molding, composite hand layup, injectionmolding, pultrusion, automated fiber placement, tube rolling, automatedtape laying, filament winding, resin transfer molding, or any suitablemanufacturing technique as is known in the art. One skilled in the artwill recognize that any suitable 3D printing technique may be used tomanufacture the components described herein.

In various embodiments, the ring may be formed into a blade root of awind turbine propeller blade. In various embodiments, the ring may beformed by composite layup.

FIG. 1 illustrates an exemplary assembly 100 for wind turbine blade rootattachment according to embodiments of the present disclosure. Theassembly 100 includes a bushing 102 that is generally cuboid-shapedhaving a cylindrical cutout 102 a on a first side, a cylindrical cutout102 b on a second, opposite side of the bushing 102, and a wedge-shapedcutout 102 c at a distal end of the bushing 102. The wedge shaped cutout102 c extends from the distal end to the proximal end of the bushing 102a distance sufficient to receive wedge 106 a (as described in furtherdetail below). In the exemplary embodiment shown, the cutout 102 cextends approximately 25% of the length of the bushing 102. In theexemplary embodiment shown, the cutout 102 c is wedge shaped, howeveralternative shaped cutouts can be employed. For example, the cutout 102c can be formed with an asymmetrical taper, or with interlockingfeatures such as a tongue-groove mating relationship with portion 106 a(which exhibits a complimentary shape).

In the exemplary embodiment shown, the cylindrical cutouts 102 a, 102 bhave substantially equal radii, though differing radii can be employedas desired. On one of the sides, the bushing 102 includes acylindrically-shaped protrusion or ear 104 extending outwardly. The ear104 can be a disc having a thickness range, and in some embodimentsinclude surface features (e.g. protrusions, etc.) for engaging theproximal end of filler 108 while still permitting relative rotationbetween the filler 108 and bushing 102. In various embodiments, the ear104 may be integrally formed into the bushing 102 by, e.g., machiningthe cutout 102 a. In some embodiments, the ear 104 can be a separatecomponent, e.g. casted, that is removably attached to the bushing toallow removal/replacement of damaged fillers 108. The radius of the ear104 is substantially equal to the radius of the cutout 102 a. Thebushing 102 further includes a threaded aperture 103 that is configuredto receive a screw for connecting the bushing 102 to a wind turbinerotor hub. As shown in the exemplary embodiment, the aperture 103 canhave a tapered opening extending along the surface of wedge 102 c. Inthe exemplary embodiment shown, the angle of the bushing is less than 20degrees, e.g. approximately 7-8 degrees. The bushing 102 is made of ametal, such as, for example, steel.

The assembly 100 further includes a core 106 that is generally formed asa first wedge 106 a and a second wedge 106 b. The core can be made ofpolyurethane foam. In some embodiments the core is constructed as asingle integral component, alternatively, the core can be formed as amulti-piece component (e.g. wedge 106 a can be separate from wedge 106 band joined at their respective apices). The thick ends of each wedge 106a, 106 b abut one another. The thin end of the first wedge 106 acorresponds to the shape of the cutout 102 c of the bushing 102 suchthat the first wedge matingly engages the bushing. The bushings 102 canbe reused in the event a core 106 is damaged. The first wedge 106 a ofthe core 106 includes a first cutout 106 c on one side and a secondcutout (not shown) on the opposite side that are shaped as conicalcutouts. When the first wedge 106 a is inserted into the bushing 102,the cutout 106 c and the cutout 102 a together form a cylindrical cutoutwith both cutouts 106 a, 102 c sharing a common longitudinal axis. Thesecond wedge 106 b includes a first cutout 106 d on one side and asecond cutout (not shown) on the opposite side that are shaped asconical cutouts. In some embodiments the core is equally tapered on thetop and bottom surfaces. Additionally, or alternatively, the core can betapered such that it lies flat against the mold surface and exhibits acomplementary/mirror contour to the mold surface. In the exemplaryembodiment shown, the core has a uniform taper for each root-insertsubassembly, however varying amounts of taper can be employed. Forexample, the cores disposed on the root insert at locations coincidingwith the high pressure side of the blade can have a lesser amount oftaper than the cores disposed on the root insert at locations coincidingwith the lower pressure side of the blade.

The assembly 100 further includes a filler 108 having a proximal,cylindrical portion 108 a and a distal, conical portion 108 b. Thefiller 108 is made of glass fiber-reinforced polymer. The filler 108 canbe formed from residual or recycled unidirectional glass fiber left overfrom the production of the blade skin. For example, FIG. 5 depicts asegment of this fiber which can be cut according to the pattern shownwhich can then be shaped, e.g. rolled up, into the desired filler shapeand size.

The bushing 102 and core 106 can be attached together as an initialsub-assembly which is then placed in mold and held in place by a rootring. Next, the filler 108 is laid down or inserted in place betweenadjacent sub-assemblies of 102/106. This process is repeated to form thecomplete ring. In some embodiments the busing 102, core 106 and filler108 are bonded together with an adhesive applied across all abuttingsurfaces. Alternatively, the adhesive can be applied only at selectlocations. In some embodiments the components are held together by thefrictional forces via an interference fit.

In accordance with an aspect of the disclosure, to form a root insertsub-assembly, a core 106 is inserted into bushing 102, with wedge 106 amatingly received by cutout 102 b. This effectively creates a unifiedpart having non-arcuate (e.g. non-cylindrical, non curvilinear) shape. Aplurality of these bushing-core units can be positioned adjacent to eachother and formed into a ring, with fillers 108 inserted/disposed betweenadjacent bushing-core units such that no gaps are formed betweenadjacent bushing-core units. As shown in FIG. 2, the inner and outercircumferential surfaces of the subassemblies, when formed into a ring,exhibit a continuous surface having a constant inner and outer diameter.

For purpose of illustration and not limitation, the core, bushing androller components disclosed herein can be formed to extend approximatelyone meter into the blade. However, alternative dimensions can beemployed as desired to accommodate different blade designs andperformance criteria. For instance, the thread can be M36, and thebushing 102 length can be approximately 0.5 meters; the core wedge canbe approximately 0.8 meters with a total length of approximately 1.2meters.

FIG. 2 illustrates a cross-section of an exemplary system 200 for windturbine blade root attachment according to embodiments of the presentdisclosure. The system 200 generally includes a plurality of the rootattachment assemblies described above with respect to FIG. 1 positionedin a ring shape. As shown in FIG. 2, the system 200 includes a pluralityof root attachment assemblies, for example, a first assembly 200 a, asecond assembly 200 b, a third assembly 200 c, etc. In particular, thefirst assembly 200 a includes a bushing 202 a, a core 206 a, and afiller 208 a. The second assembly 202 b similarly includes a bushing 202b, a core 206 b, and a filler (not shown). The third assembly 202 csimilarly includes a bushing 202 c, a core 206 c, and a filler (notshown). The filler of the second assembly matingly engages the cutoutsof the first assembly 202 a and the second assembly and, with the ear ofthe second assembly 202 b, fills the void space between the firstassembly 202 a and the second assembly 202 b. In a similar fashion, thefillers for each of the adjacent assemblies around the ring fill thevoid space between the two assemblies. In some embodiments, adjacentassemblies (e.g. 200 a, 200 b) can be configured to permit relativemovement therebetween over a first range of motion (e.g. from zerodegrees, or coplanar, to 45 degrees with the horizontal plane of theadjacent assembly), and thereafter lock in place to prohibit furtherrelative movement therebetween. This can simply manufacturing in that itallows a plurality of assemblies of respective bushings, wedges andfillers to be assembled on a flat surface, and thereafter bent orrotated to bring the ends of the assembly into engagement to form a ringstructure. During manufacturing, the mold can receive approximately 10layers of layup segments (e.g., glass fiber) and then the rootattachment of the present disclosure is inserted, thereafter anotherapproximately 10 layers of layup segments are applied on top of the rootattachment. In some embodiments, a plurality of layers of rootattachments can be employed, with varying layers of layup disposedtherebetween.

FIG. 3 illustrates a method 300 of forming a wind turbine rootattachment system according to embodiments of the present disclosure. At302, a plurality of assemblies is provided. Each of the assembliesincludes a bushing comprising a body having a proximal end and a distalend, a first cutout extending from the proximal end to the distal end ona first side of the bushing, a second cutout extending from the proximalend to the distal end on a second side of the bushing and a core cutoutat the distal end, and an ear disposed at the proximal end of thebushing and within the first cutout. Each of the assemblies includes acore having a proximal end and a distal end, the core comprising a firstwedge and a second wedge distal to the first wedge, each wedge having athick end and a thin end, wherein the thick end of the first wedge abutsthe thick end of the second wedge, the thin end of the first wedgedisposed within the core cutout, the core comprising a third cutoutextending from the proximal end to the distal end on a first side of thecore and a fourth cutout extending from the proximal end to the distalend on a second side of the core. Each of the assemblies includes afiller disposed within the first filler cutout and the third fillercutout, the filler contacting the ear. At 304, the filler and the ear ofa first assembly of the plurality of assemblies are engaged into thesecond cutout and the fourth cutout of a second assembly of theplurality of assemblies. At 306, the plurality of assemblies is formedinto a ring.

In various embodiments, the ring may be formed into a blade root of awind turbine propeller blade. In various embodiments, the ring may beformed by composite layup.

The descriptions of the various embodiments of the present inventionhave been presented for purposes of illustration, but are not intendedto be exhaustive or limited to the embodiments disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the describedembodiments. The terminology used herein was chosen to best explain theprinciples of the embodiments, the practical application or technicalimprovement over technologies found in the marketplace, or to enableothers of ordinary skill in the art to understand the embodimentsdisclosed herein.

What is claimed is:
 1. A wind turbine blade assembly comprising: abushing comprising a body having a proximal end and a distal end, afirst cutout extending from the proximal end to the distal end on afirst side of the bushing, a second cutout extending from the proximalend to the distal end on a second side of the bushing and a core cutoutat the distal end, and an ear disposed at the proximal end of thebushing and within the first cutout; a core having a proximal end and adistal end, the core comprising a first wedge and a second wedge distalto the first wedge, each wedge having a thick end and a thin end,wherein the thick end of the first wedge abuts the thick end of thesecond wedge, the thin end of the first wedge disposed within the corecutout, the core comprising a third cutout extending from the proximalend to the distal end on a first side of the core and a fourth cutoutextending from the proximal end to the distal end on a second side ofthe core; and a filler disposed within the first cutout and the thirdcutout, the filler contacting the ear.
 2. The assembly of claim 1,wherein the bushing comprises a metal.
 3. The assembly of claim 2,wherein the metal is stainless steel.
 4. The assembly of claim 1,wherein the filler comprises a composite material.
 5. The assembly ofclaim 4, wherein the composite material comprises glass fiber reinforcedpolymer.
 6. The assembly of claim 5, wherein the glass fiber reinforcedpolymer comprises unidirectional fibers.
 7. The assembly of claim 1,wherein the core comprises a foam.
 8. The assembly of claim 7, whereinthe foam comprises polyurethane.
 9. The assembly of claim 1, wherein thecore cutout comprises a wedge-shaped cutout.
 10. The assembly of claim1, wherein the core cutout comprises an aperture.
 11. The assembly ofclaim 1, wherein the first cutout and the second cutout each comprises acylindrically-shaped cutout.
 12. The assembly of claim 1, wherein theear comprises a cylinder.
 13. The assembly of claim 1, wherein the thinend of the first wedge is disposed within the core cutout.
 14. Theassembly of claim 1, wherein the filler comprises a first portion havinga cylindrical shape and a second portion having a conical shape.
 15. Theassembly of claim 14, wherein the first portion of the filler isdisposed within the first cutout and the second portion of the filler isdisposed within the third cutout.
 16. A system for wind turbine rootattachment, the system comprising: a plurality of assemblies of claim 1arranged in a ring; wherein the ear and the filler of a first of theplurality of assemblies engages the second cutout and the fourth cutoutof a second of the plurality of assemblies.
 17. The system of claim 16,wherein the plurality of assemblies form a ring.
 18. The system of claim17, wherein the ring is disposed within a wind turbine propeller root.19. A method of forming a wind turbine root attachment system, themethod comprising: providing a plurality of assemblies, each assemblycomprising: a bushing comprising a body having a proximal end and adistal end, a first cutout extending from the proximal end to the distalend on a first side of the bushing, a second cutout extending from theproximal end to the distal end on a second side of the bushing and acore cutout at the distal end, and an ear disposed at the proximal endof the bushing and within the first cutout; a core having a proximal endand a distal end, the core comprising a first wedge and a second wedgedistal to the first wedge, each wedge having a thick end and a thin end,wherein the thick end of the first wedge abuts the thick end of thesecond wedge, the thin end of the first wedge disposed within the corecutout, the core comprising a third cutout extending from the proximalend to the distal end on a first side of the core and a fourth cutoutextending from the proximal end to the distal end on a second side ofthe core; and a filler disposed within the first cutout and the thirdcutout, the filler contacting the ear; engaging the filler and the earof a first assembly of the plurality of assemblies into the secondcutout and the fourth cutout of a second assembly of the plurality ofassemblies; and forming the plurality of assemblies into a ring.
 20. Themethod of claim 19, further comprising forming the ring into a bladeroot of a wind turbine propeller blade.